Photoacoustic Detector: PA201S  

Custom photoacoustic gas cell for laser sources 

Laser photoacoustic spectroscopy (LPAS) is a highly attractive method for the trace gas analysis due to the high sensitivity, linearity and low sample gas volume. Tunable laser sources provide high selectivity and high measurement accuracy due to the zero background nature of the measurement principle.

The use of the novel cantilever optical microphone provides unmatched sensitivity and enables measurements in low pressures without compromising on the sensitivity. Narrower spectral lines at lower pressures provide additional benefit for selectivity compared to other tunable laser based systems operating at ambient pressure.

Gasera’s PA201 research gas cell is designed for laboratory measurements and can be tailored for different types of light sources such as the near infrared distributed feedback laser (DFB), the quantum cascade laser (QCL) and the optical parametric oscillator (OPO).

Ultra-sensitive optical microphone 

The heart of the system is the patented optical microphone comprising of a MEMS cantilever sensor coupled with a laser readout interferometer that can digitally measure microscopic movements of the cantilever sensor, having a dynamic range greater that any analog circuitry can ever obtain.

The cantilever-type pressure sensor is designed to significantly improve the sensitivity of PAS. An extremely thin cantilever portion moves like a flexible door due to the pressure variations in the surrounding gas. The movement of the free end of the cantilever can be about two orders of magnitude greater than the movement of the middle point of the tightened membrane under the same pressure variation. This is because the cantilever only bends and does not stretch.

Features 特性

lPhotoacoustic detector with cantilever enhanced optical microphone

lVirtual zero-background measurement principle

lTotal gas volume of the system is low, approx. 30 ml

lThe gas exchange procedure is user configurable by a simple user interface with display and buttons. The gas exchange can be started manually with a press of a button or the instrument can be programmed to do it automatically using timer or an external trigger.

lThree gas connections in the front. The sample gas has two connections, one for input and one for output. The input is equipped with a particle filter.

lGas cell is stabilized to 50 °C temperature.

lPatented ultra-sensitive optical microphone based on a MEMS cantilever sensor coupled with a laser interferometer to measure microscopic movement of the cantilever sensor.

lComplies with the following standards or other standardization documents under the Low Voltage Directive 2006/95/EC and EMC Directive 2004/108/EC: EN 613261:2005, EN 61010-1: 2001.

l12 months warranty

Technical specifications

lMaterials in contact with gas:

FPM (seals, solenoid valves)

NBR (solenoid valves, gas connectors)

PPA, PBT (solenoid valves, gas connectors)

PPS, EPDM (gas pump)

Stainless steel (solenoid valves, gas connectors)

IR-window of the cell: BaF2, KBr, ZnSe etc.

Nickel (gas exchange unit block, gas connectors)

PTFE (tubes, particle filters)

PP (particle filters)

lDimensions of the PA201 module: 17.2 cm W x 10.5 cm H x 34.9 cm D

lWeight: approx. 5 kg

lTotal internal gas volume: 30 ml

lOperational conditions:

Temperature range: 15 °C – +35 °C

Humidity range: Below 90% RH, non-condensing

Pressure range: Ambient level

Dust/water resistance: IP20 (IEC 529)

Shock/vibration endurance: Strong vibrations can affect the measurement results. Acoustical level: Loud sounds can affect to the measurement results

lStorage conditions: Temperature range: 0 °C – +60 °C

lSample gas conditions:

Temperature: Below the gas cell temperature and noncondensing

Pressure: 930 mbar – 1100 mbar

Moisture: Non-condensing at sample temperature

Gas flow with bypass flow: approx. 1 liters/minute Particulates size < 1 μm

lGas connections: Tube fittings for 6/4 mm tubing

lElectrical connections:

Power supply unit:

Input voltage: 100 - 240 Vac, 50 - 60 Hz

Input power max: 30W

Analog outputs:

Output connectors: BNC or D9 connector

Output signal voltage span: ± 3.3 V

Output signal frequency band: Low pass filtered, 0-10kHz

Output load: >2k resistive

Trigger I/O:

CMOS compatible input

Open collector output

Triggering sequence programmable

lMeasurement specifications:

Detection limit: Gas and light source dependent. Typically in the low ppb -region.

Optical path length: 100 mm at optical axis

Repeatability: < 1 % of measured value in operational conditions at the calibration concentration (source dependent)

Temperature stability: Ambient temperature change within the operational temperature range will not cause drift. The measurement pressure can be selected between 300 mbar - 1000 mbar.